DENVER — Josh Duignan got his first flu shot last year when his wife was pregnant with their first child. While son Ethan will get a shot this year, Duignan isn’t sure whether he’ll also get a chance to roll up his sleeve.

Health officials nationwide are urging healthy adults and schoolchildren to skip the shot because British regulators have shut down a major flu-shot supplier. The news carries particular concern in Colorado, which was the epicenter of last year’s flu season with 12,885 reported cases and the deaths of 12 children.

With 46 million doses now unavailable, the government says the 54 million flu shots left from a rival firm should be reserved for youngsters ages 6-23 months, people 65 or older, anyone living with babies younger than 6 months and others in high-risk groups.

Duignan knows his pediatrician has enough doses to vaccinate Ethan, now 7 months, but isn’t sure whether he will get a shot.

If they turn me down, I don’t know what I’ll do,” he said. “But I’m going to get one this year. I promised my wife I would.”

The shutdown of flu vaccine production at Chiron Corp. has slashed supplies across the nation. Public health clinics in Georgia and Pennsylvania will lose nearly a third of their doses. Minnesota canceled flu clinics for state employees and set aside vaccines for those at high risk.

“Worst-case scenario, we will have probably more patients being hospitalized with pneumonia,” said Dr. Wellington Liu, medical director of Kateri Medical Residence in New York City, a nursing home with 440 long-term patients.

Memories of last seasonDoctors at Arvada Pediatric Associates in suburban Denver normally recommend flu shots for siblings of children with asthma and other risky conditions. But even those children are expected to forgo shots this year, president Charyl LeBlanc said as the office fielded calls from panicked parents.

“It’s been a wild day,” LeBlanc said Wednesday. “Part of the problem is everybody is remembering the flu season last year, particularly in Colorado.”

Colorado health officials do not track how many doses are available statewide, although Chiron rival Aventis Pasteur did send 100,000 doses for a vaccination program targeting low-income children.

“It’s kind of disappointing that we didn’t have more than two sources to get the vaccine,” complained Dan Knuth, 59, of New Brighton, Minn., who said he probably won’t get a shot this year. “It shows the vulnerability of our health care system.”

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Kaiser Permanente, the nation’s largest health maintenance organization, has between 40,000 and 50,000 doses left for Coloradans, but those may be nearly gone by Saturday, said Eric France, chief of preventive medicine for the HMO in Colorado.

“My reaction was, ‘Here we go again,”’ France said. “We’ve had five years of trouble with the vaccine supply. ... Doctors, nurses and patients are saying, ‘Why can’t we get it right?”’

The Visiting Nurse Association of Denver, supplied by Chiron, originally hoped to vaccinate about 70,000 people this season, but that number will probably be less than 10,000, spokeswoman Martha de Ulibarri said.

With a 7-month-old baby, Barbara Askenazi said she planned to call her pediatrician to see whether her she and her 2½-year-old son Buddy, who mixes with plenty of children at nursery school, should get shots anyway.

“It just dumbfounds me that they can’t figure out how to make enough,” said Askenazi, 36. “People know the flu is coming, they know how dangerous it is, but there’s always a shortage of vaccine.”

High-risk patients depend on flu shots because the injections are made of killed influenza virus. Other people have another option: About 1 million doses of an inhaled flu vaccine, MedImmune Inc.’s FluMist, will be available for healthy 5- to 49-year-olds. It’s made from live but weakened influenza virus.

Voluntary rationing urgedHealth care workers can’t legally bar insistent, lower-risk patients from getting shots but will try to persuade them to do otherwise.

“Every person of average risk who gets a shot is taking a shot away from someone who really needs it,” France said.

Officials have discussed the possibility of diluting the flu vaccine, but there’s no data on whether that would still protect high-risk groups. Plus, most shots come in with a single syringe and cannot be used by two people.

In Maryland, Montgomery County ordered all of its adult vaccines from Chiron and is left with only child vaccines this season, said Ulder Tillman, county health officer. Plans to vaccinate about 4,000 people this year have been halved.

The vaccine shortage will also have economic impacts. The Minnesota Visiting Nurse Agency counts on proceeds from its flu clinics to help fund some 80,000 home visits a year. It expected to receive 150,000 doses this year from Chiron.

“We had to cancel everything,” said Mary Ann Blade, the agency’s chief executive.